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Man arrested over American woman's death in Florence had met her in nightclub

Police believe pair had consensual sex at her apartment before she died

Suspect's DNA was found in Olsen's apartment, and he also had victim's phone

(CNN)A man has been arrested in connection with the death of Ashley Olsen, a 35-year-old American artist living in Florence, the city's chief prosecutor told reporters Thursday.

The suspect, Cheikh Tidiane Diaw, was arrested at his home Wednesday night, chief prosecutor Giuseppe Creazzo announced at a press conference.

DNA evidence linked to the suspect was found in a condom and on a cigarette at Olsen's house, where Diaw's fingerprints were also found, Creazzo said. Diaw had taken Olsen's phone and put his SIM card in it, and was using the device when he was arrested, the prosecutor said.

A photograph released by Italian police of suspect Cheikh Tidiane Diaw.

Police believe that Olsen and Diaw, an illegal immigrant from Senegal who was born in 1988, had met at the city's Montecarla nightclub and left to go back to Olsen's place together, where they had consensual sex, Creazzo said.

He said Olsen was strangled by something "other than bare hands," but also had two fractures to her cranium.

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Police have established there was no one else present in the room when Olsen died, Creazzo said. Authorities are awaiting the results of toxicology tests.

Olsen was found dead in her apartment on Saturday, after her boyfriend had been unable to reach her and asked Olsen's landlord, Claudia Colivicchi, who lived upstairs, to open the apartment for him.

Colivicchi told Italian media outlets that when she opened the door, Olsen was on a bed in a mezzanine loft of the studio apartment.

Olsen's dog, Scout, who was a regular feature on her Instagram and Facebook feeds, had defecated in multiple places within the apartment, indicating that the well-trained beagle had not been taken for a walk in some time, Colivicchi told media outlets.

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Olsen was originally from Summer Haven, Florida. She was living in Florence, where her father, an architect, works at an art school. Her father was seen with friends outside her building Monday, leaving flowers.

"The police haven't really said anything yet. My son is waiting for the police to share more," Olsen's grandmother, Ann Olsen, told CNN by phone from Florida.